The DNA within just about every living cell contains all the information necessary to build an entire living organism. A library also contains a lot of information. The information in a library does no good to anyone unless the books are read. The same thing is true for DNA -- without being read, it doesn't do any good. So there are some obvious parallels between a library and a cell's DNA. But there are some significant differences, too.

Information in DNA

DNA consists of a chain of nuclear bases -- adenine, thymine, cytosine and guanine, usually abbreviated A, T, C and G. The order of those bases determines the structure of your proteins. That's because three-base sections -- called codons -- will direct the addition of an amino acid. Proteins are built with the addition of one amino acid after another, so DNA is like an assembly manual in which every word contains three of four possible letters.

Organizing DNA Information

The sections of DNA that direct the building of a protein are called genes. Each gene could be compared to one assembly manual. Genes are organized in long strings, called chromosomes. If a gene is an assembly manual, then you can think of each chromosome as a shelf in a library. All the chromosomes together are like a library full of shelves.

Getting DNA Information Out

DNA in complex organisms -- such as you -- is kept in a separate compartment in the cell. That's the nucleus. Proteins are built outside of the nucleus, so DNA information needs to make it out of the nucleus. But the DNA won't move. So if the nucleus is the library building then there's one more important step. Somebody needs to make a copy of the pages of a book and bring it out of the library. In the cell, the copy that goes in and out of the nucleus is called messenger RNA. So genes are like books, chromosomes are like bookshelves, the set of an organism's chromosomes are a library full of shelves, the nucleus is like the library building and messenger RNA is like a copy of a book.

Not a Library

Of course, DNA is not really like a library, even with all those similarities. One of the biggest differences is a very basic one. The books in a library have their information printed on pages. DNA doesn't have one part carrying information; it is the information. It's as if a book was built only out of letters chained together instead of printed on paper. The same with the messenger RNA -- it wouldn't be like a copy printed on paper, it would be another string of letters chained together.

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About the Author

First published in 1998, Richard Gaughan has contributed to publications such as "Photonics Spectra," "The Scientist" and other magazines. He is the author of "Accidental Genius: The World's Greatest By-Chance Discoveries." Gaughan holds a Bachelor of Science in physics from the University of Chicago.